Figure 4. Comparisons of six parameters (mean ± Standard Error) in Berberis julianae to examine the effects of stamen movements on insect visitor foraging behavior and their roles in pollination.

The major pollinator, Apis cerana, was studied in 2020 and 2021 under open pollination (far left) and enclosed conditions (set-up shown in Figure 1—figure supplement 1 and Video 3), whereas the anthophorid bee pollinators and the two flies (Meliscaeva spec. and Rhingia campestris) were compared under enclosed conditions in 2021. Different lowercase letters above error bars indicate significant differences between control (stamen mobile [SM]) and alcohol-treated (stamen immobilized [SI]) flowers. (A′–D) Visitation rates of four visitor species, showing that A. cerana visited control flowers more frequently than SI flowers under open pollination (A′), but no visitor species discriminated between SI and SM flowers under enclosed conditions (A–D). All visitor species spent more time (E′–H) and touched more stamens (I′–L) in SI flowers than in control SM flowers. Visitors removed more nectar from SI flowers, resulting in less nectar remaining per flower (M′–P). Pollen removal by A. cerana was lower from SI than from SM flowers (Q′, Q), but higher in the other three visitor species (R–T). Compared to SM flowers, pollen transfer efficiency was significantly decreased in SI flowers (U′, U, V, X), although it did not differ in Meliscaeva spec. (W). Sample sizes (n) are given in brackets.